Slowly but surely, Retina-enabled apps for the new MacBook Pro are starting to hit the market -- and that trickle should grow into a flood as the summer turns into fall.

Last month's launch of the MacBook Pro with Retina display initially caught third-party software developers flat-footed; their apps weren't ready for the laptop computers new high-resolution display. (Apple, of course, was first out the door with Retina-ready upgrades of iPhoto Aperture ( Macworld rated 4 out of 5 mice )and Final Cut Pro X.) But now developers are beginning to catch up with the new screen.

Updated titles that have been released in the month since the Retina MacBook Pro was unveiled include popular productivity apps such as Reeder (Macworld rated 4 out of 5 mice), Sparrow (Macworld rated 4 out of 5 mic ), and Twitteriffic. We've also seen a handful of Retina-ized games from vendors such as Aspyr -- including titles from the popular Call of Duty and Star Wars franchises. (See below for a more complete sampling of updated apps.)

And more are on the way. Macworld contacted two dozen app developers this week to check the status of the updating efforts. Most said they were on the verge of releasing Retina-enabled updates for their softwarebut companies with multiple titles said those upgrades would be rolling out slowly over the next few months.

It takes time

"Being a small company we can't devote the resources to update everything all at once," said John Champlin, a spokesman for Ambrosia, "So we are prioritizing our product line up and have begun updating what we can, as quick as we can." Champlin says there will be an upgrade of the company's Snapz Pro X screen-capture software in the very near future.

Champlins comments were echoed by other developers, most of whom declined to give a firm date for launching higher-resolution apps.

"We'll roll them out one product at a time," said former Macworld contributor Rob Griffiths, now at app-maker Many Tricks. His company offers 10 different desktop apps, which complicates the process. "The logistics of doing them all at once are overwhelming," Griffiths said.

Developers said they welcome Retina. "High-resolution is pretty awesome, and I can't wait for it to be in every machine," said Flying Meat's Gus Mueller, who has released upgraded versions of Acorn (Macworld rated 3 out of 5 mice) and VoodooPad (Macworld rated 4 out of 5 mice).

Upgrading to a Retina display, however, involves more than plugging in a few simple bits of code.

"The challenges vary in supporting the Retina display from title-to-title, including slow-down at higher resolutions, UI changes needed to support the higher resolutions, and overall implementation of the higher resolution in games where it doesn't exist," Aspyr spokesperson Elizabeth Howard said via email. "Each scenario requires differing development support."

Realmac's Nik Fletcher pointed to several challenges he faces in upgrading offerings like RapidWeaver (Macworld rated 4.5 out of 5 mice). "One is working with pixel-based media (images) and ensuring that it displays accurately and translates across pixel densities," he said. "The other being that Retina-enabled Macs can obviously have non-Retina-enabled displays attached. so you need to also ensure that the UI updates when dragging between Retina and non-Retina displays."

It isn't simple

Another challenge: Developers are juggling other updates as well.

"Ideally, I would love to roll out a single update with all the graphics Retina-ready in one go, but given that Mountain Lion is out in the next couple of weeks, and we are unlikely to have all the toolbar icons completed by then, it will probably be done over a couple of updates," said Literature & Latte's Keith Blount, developer of the Scrivener writing program (Macworld rated 4.5 out of 5 mice). "We expect to be completely Retina-ready within the next month or so, though."

That makes for a hectic development process.

"I remember back in the day when Apple would announce something at WWDC and a company would have several months to figure out a strategy and prepare their apps for updating," said Michael Wray, president of Mariner Software. "Today, while developers do get informed, it's a hell of a lot quicker turnaround that's expectedboth by Apple and the public."

Not every developer is sure of the benefit. "Certainly we like having better-looking apps, and users like that too, but it's unlikely to actually generate more sales the way adding new features do," said Paul Kafasis of Rogue Amoeba. "Apple's moved the goalposts for everyone, and we've all got to play catch-up. That's definitely challenging."

But other developers say the challenge comes with some upside.

"The Retina display upgrades have allowed our developers the opportunity to go back and look under the hood of our products, and with the new tricks and skilled learned at WWDC, we are hoping to see improved results on a varied list of things," said Ambrosias Champlin. "So, in short we are excited to get a chance to go back in and tweak and rework an already loved product."

And the end result, developers say, should be great to look at.

"We're not necessarily excited about the process," said Many Trickss Griffiths, "but we do like the fact that our apps will look better on the Retina MacBook Pros."

High resolution

Here is a list of some of the Mac apps that have been upgraded to support the new MacBook Pros Retina display. (Note: Some of them have not yet been approved for the Mac App Store.)